The definition of “mobile computing” has evolved, and continues to evolve, in step with the advances that are occurring in mobile communications. In the 1990's, mobile computing would likely have described merely the use of a laptop computer. A laptop computer gave the computer user the ability to easily transport a keyboard, monitor, computer processor and memory from one location to the next so that multiple desktop computers (e.g., one at the office and one at home) were not necessary. Battery-powered laptop computers made it possible for the user to operate the computer at locations away from regular A/C power sources, such as on a plane or train, or at a remote location (e.g., a construction work site).
As computer networking developed, mobile computing took on a slightly new meaning. With the ability to connect to an office network using a modem and telephone line connection, a user was able to access a centralized network from remote locations. Thus, mobile computing could involve a laptop connected from a telephone line in a hotel room in New York to a network system of a corporate headquarters in Tokyo, Japan. The user could then disconnect the telephone connection, travel to Chicago, set up the laptop in a similar fashion and communication with the Tokyo office via a phone line connection from a hotel room in Chicago.
Along the way, cellular telephony became commonplace. Using cellular telephones, a user could travel from place to place with a wireless connection to the telephone system, so that, regardless of location, they could be reached at a single telephone number and could carry on the communication while moving from one location to another. It was only a matter of time before mobile computing would seek to have the same kind of connectivity.
Today, mobile computing includes the continuous wireless connectivity to an IP-based network with the ability to roam from point A to point B while maintaining the connection and ability to communicate over the connection. To assist in the development of mobile IP, the Internet Engineering Task Force (IETF) developed and continues to develop a set of protocols, referred to as “RFCs”, governing mobile IP operation. These protocols establish a system for keeping track of mobile systems (“mobiles”) in a wireless IP network, allowing a mobile to change its “point of attachment” to the network without losing its ability to communicate over the network. The most recent RFC related to tracking mobiles in a wireless IP network, RFC 3344, which updates and obsoletes RFC 3344, which updated and obsoleted RFC 2002.
These protocols, among other things, established a system whereby each mobile node uses two IP addresses: a fixed home address and a “care-of” address that changes at each new point of attachment. Through the use of a router associated with the home address (called a “home agent”) and routers associated with the care-of addresses (called “foreign agents”), the location of the mobile node can be established, and datagrams and other forms of data destined for a particular mobile node at its fixed home address can be forwarded to the care-of address that has been associated with that fixed home address.
The system described in RFC 3344 is well known and operates adequately. However, mobile IP, as it exists in the RFCs today, requires that a registration procedure be performed by the roaming IP device with the “active” foreign agent (the foreign agent with which a particular roaming IP device is registered at a given time). This registration process uses precious RF bandwidth. Accordingly, it would be desirable to have a mobile IP system whereby the use of RF bandwidth for registration is minimized.